of worcester



May 2 1931. H. w. H. BET'H SEGMENTAL GRINDING WHEEL AND METHOD OF MAKING THE SAME Filed Dec. 21, 1928 Fig WlTNEssEs 6. H. GM M47 1.

Patented May 26,1931

UNITED STATES PATENT orFlcr.

HUGO W. H. BETH, 0F WORCESTER, MASSACHUSETTS, ASSIGNOR TO NORTON COMPANY, OF WORCESTER, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS SEGMENTAL GRINDING WHEEL AND METHOD OF MAKING THE SAME Application filed December 21, 1928. Serial No. 327,620.

This invention relates to grinding Wheels and to a method of making the same, and more particularly to a segmental wheel made up of a rotatable support on which abrasive segments are secured.

A grinding wheel of the type shown in the patent to Greenwood No. 1,469,723 comprises a rotatable support on which an annulus of separately fashioned abrasive segments are mounted and clamped in position. These segments are made of selected sizes of abrasive grains bonded together by ceramic materials which have been vitrified to a glassy or porcelanic condition. Such an abrasive body is comparatively brittle and fragile and it may be easily broken under the forces which are met in some types of grinding operations, such as grinding wood pulp. If the wheel is intended for such severe usage, it is very important that the segments fit accurately on their support and that the area of contact therebetween be so large that any stresses incident to clamping the segments in 'place or to the act of grinding will be distributed widely. Otherwise the relatively fragile material of which these abrasive segments are ,made may be broken when the wheel is put into use.

Various expedients have been proposed heretofore for seating the abrasive segments on their support, and it is the main purpose of this invention to provide a simple form of grinding wheel in which the segments are provided with shoes or faces contacting with the segments throughout a large area and which likewise fit the surface of the supporting member, and thereby to provide a grinding wheel structure made up of abrasive segments which are accurately and correctly mounted on a rotatable support and which may therefore beclamped rigidly in place and held securely under the stresses of a grinding operation. J

A further object is to provide a simple and economical method of producing a segmental wheel of this type.

With these and other objects in view, as will be apparent to one skilled in the art, the invention resides in the combination of parts and the steps of a process set forth in the accompanying description and covered by the claims appended thereto.

A segmental grinding wheel made in accordance with this invention comprises a rotatable support on which abrasive segments are secured; and in order that the segments may be seated firmly and correctly on the support, each segment is provided with a facing or shoe which unites firmly with the rough or porous surface of the segment and which will fit against the supporting surface of the rotatable support. To this end, each segment is formed with a facing of a moldable self-hardenin material, and preferably a material capa le of being shapedas a plastic mass and of thereafter setting or hardening to a rigid body, such as one of the various types of cement. This plastic mass is molded in position on the abrasive segment and against the supporting member so that it will fit the surfaces of both. Thereafter the segments are adjustably secured to the support.

Referring to the drawings which illustrate one embodiment of the invention:

Fig. 1 is a fragmentary sectional view of a grin ing wheel; and

Fig. 2 is a perspective view, partly broken away, of a segment ready for mounting on its rotatable support.

A segmental grinding wheel embodying this invention may comprise a central rotatjable support 10 which may be made of iron or other suitable material and which has an outer peripheral surface 11 of cylindrical or other form; and on this drum a plurality of abrasive segments 12 are mounted to form a grinding annulus. There may be one or more rows of segments on the drum as illustrated in the prior patentto Greenwood. Ojne suitable manner of fastening these segments in position involves the use of wedge blocks 15 Which are inserted in grooves 16 between adjacent inner faces of the segments; and these grooves are provided with beveled shoulders 17 corresponding with the sloping faces of the clamping blocks, whereby the clamping blocks may be automatically adjusted to the two opposed shoulders'on the adjacent segments and thus serve to secure the segments in place. The clamping shoulders of the segments are preferably provided with shoes 18 of metal or other suitable material which afford smooth faces capable of forming bearing surfaces for the clamping wedge blocks. The shoes may be cast or otherwise molded on the shouldereither before or after the segment has been assembled in place. In order to secure each wedge block adjustably to the drum, bolts 20 are provided; and each of these is threaded at one end into the clamping block, and at the other end it is secured by means of nuts 22 to the inner face of the drum through which the bolt passes. If desired, the bolt 20 may be made of an elastic material which will permit expansion of the abrasive annulus due to temperature changes. Since the clamping pressure of the wedge block on the shoulders of the segments is exerted inwardly toward the center of the drum, it is desirable that this pressure be distributed throughout a considerable contact area between each segment and the drum. It has been proposed heretofore to mold metal shoes on the bottoms of the segments, and this has been done by casting the metal in a mold fastened on the segment and which has a shaped surface corresponding to the curvature of the drum. A considerable problem has been involved in forming these shoes, since it has often been found desirable to lap or otherwise finish their surfaces after the casting operation so that they would fit the drum more accurately than could be obtained by the casting process alone. This has involved a considerable labor expense as well as loss of time, and has rendered it uneconomical to have the shoe engage the whole surface of the drum.

It is accordingly a primary feature of this invention to provide a shoe or seat for the abrasive segment which may be easily and simply manufactured and which will fit the drum surface and so seat the segment correctly. To this end, I propose to provide a seat or shoe 25 for the segment by casting or molding it onto the porous face of the segment and utilizing the surface 11 of the drum itself for the mold, so that when the shoe has been shaped to the drum surface it will fit accurately thereon. The shoe is made of a material capable of being molded directly on the drum surface and which will unite with or adhere to or otherwise make contact with the abrasive body throughout a large area, and it ispreferably a cementitious material, such as hydraulic cement, which is capable of being put in place as a plastic body and then setting to a hard and durable body.

Of the various methods which may be utilized for forming this shoe, it is preferable to employ a process of the following steps. -After the abrasive segment has been manufactured by standard methods and suitably shaped for assembling with other segment-s to form an abrasive annulus having an outer cylindrical surface, or other suitable shape, the under or inner concave face 24 of the-segment is provided with a comparatively thick coating of cement wetted with a little water to form a thick mass of butterlike consistency, so that it will adhere to the segment. The'segment is then placed directly on the drum in correct position for mounting so that the cement will contact with the drum and so be molded to the shape of the drum surface and thereby fit it accurately to form a bearing seat for the removable segment. The cement will moreover permeate the surface pores of the abrasive segment and so unite the shoe intimately and integrally therewith. It is, of course, understood that such abrasive segments are made of suitable abrasive grains, such as crystalline alumina or silicon carbide, held together by suitable bonding materials, such as a vitrified ceramic material, and that this bond does not fill all of the spaces between the grains but leaves voids or pores therebetween. If desired, the surface of the abrasive stone which is to carry the cement shoe may be made impervious to water by a coating of varnish or the like. This serves the useful function of preventing the water from being absorbed rapidly from the cement and into the pores of the stone and thus drying the cement too rapidly. This coating is preferably so thin that it will not prevent the cement from adhering to the pores or the rough surfaces of the abrasive stone.

In order to insure having the cement facing or shoe 25 of the right thickness, it is advisable to place small shoes 26 of compressible material on the segment, such as may be accomplished by gluing four small pieces of leather on the concave face of the segment near its corners; and these serve as temporary seats to hold the segments properly spaced from the drum. \Vhen the segments buttered with the cement have been placed on the drum, the wedge blocks may be tightened in place and the leather shoes drawn securely into contact with the drum. -Any surplus cement will spread out and escape from the sides, and the cement shoe will thus make complete contact both with the drum and with the porous surface of the segment. The cement will not make an integral union with the drum because of the fact that the cement does not adhere as firmly thereto as it would to the abrasive segment; hence, if desired, the abrasive segment may be at any time removed from the drum.

After the cement has hardened, the segmen s may be removed for storage and then later reassembled on the drum and preferably in the same position in which they were first mounted; but if desired the segment may be permitted to remain on the drum without dismantling. In the latter case, the wedge blocks will be further tightened after the cement has been fully set, in

order to .take up any slight play caused by shrinkage of the cement, and thereby force the segments securely and tightly against the supporting surface of the drum with each shoe bearing directly on that portion of the drum to which it has been molded. After this has been accomplished, the wheel may be further treated as desired, and this may involve filling the crevices between the seg ments with a suitable filler 28 which holds the segments rigidly in position against forces tending to move them laterally. A suitable filler for this purposeis a low melting Babbitt metal or various other fillers such as a mixture of sulfur and ground coke, which is known as lavasul. It is preferred, however, to utilize the metal and to pour this into position in the molten state so that it will unite firmly with the porous surfaces of the segments and form a rigid and unitary structure thereof.

It will be apparent that, in accordance with this invention, I have done more than merely placing a cement filler between the segment and the drum but that I have provided a way whereby the segments may be correctly fitted to the drum and the outer convex surfaces of the various segments may be aligned properly to form a true cylindrical surface. Moreover, the segments and their shoes are so shaped that they will not be skewed or otherwise twisted or improperly positioned when later mounted on the drum. This construction insures that the wedge blocks will fit against the shoulders of the segments correctly and that the stresses will be evenly distributed from the wedge blocks to the segments. Moreover, the cement shoes on the bottoms of the segments will contact throughout their maximum area with the drum and so distribute the clamping pressures more widely than would be otherwise possible. It will also be understood that various equivalent materials may be substituted for the cement herein described, it being desirable that the material be one capable of being molded as a soft or plastic body to the-shape of both the segment and the support on which the segment is mounted, and that this plastic material set or harden, and preferably without the application of any considerable amount of heat, and thereby form a solid shoe or seat for the segment which has a large area of contact with both abrasiveand support. It will also be noted that leather pieces are used for the temporary shoes, since leather is compressible and will not interfere with the final operation of clamping the segments tightlv on the support.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The method of making a grinding wheel having abrasive segments 1 adjustably clamped on a rotatable support comprising the steps of locating thesegments in an ap proximately correct grinding position on the support, providing a layer beneath the segments of a moldable material capable of setting to a hard body, forcing the material into full contact with the adjacent faces of the segment and the support, permitting the moldable material to harden in place and thereafter drawing the segments down firmly onto the support.

2. The method of making a grinding wheel having abrasive segments adjustably clamped on a rotatable support comprising the steps of providing the inner face of each segment with a layer of a cold setting cement, locating each segment on the support in an approximately correct grinding position and causing the cement to shape itself to the adjacent face of the support, permitting the cement to harden and thereafter clamping the segments tightly in position.

3. The method of making a segmental grinding wheel comprising the steps of providing the segments with spaced temporary shoes, mounting the segments with these shoes in contact with the support, providing between the segment and the support a layer of a moldable material capable of hardening and causing it to conform to the shapes of the adjacent faces thereof, permitting the moldable material to harden and thereafter clamping the segments to the support with each shoe bearing directly on that portion of the support to which it has been molded.

4. The method of making a grinding wheel having an annulus of abrasive segments adjustably secured on a drum, comprising the steps of providing the inner face of each segment with a coating of a cold setting, plastic cement, placing each segment onthe drum with temporary shoes therebetween, securing the segments in approximately the corrgct grinding position and forcing the cement into full contact with the drum, permitting the cementto set, and thereafter adjustably securing the segments on the drum with each shoe bearing directly on that portion of the drum to which it has been molded.

5. A grinding wheel comprising a rotatable support, a plurality of abrasive segments thereon, each segment having spaced locating shoes of compressible material thereon and a shoe molded to that portion of the support beneath on which it rests, and means for clamping the segments securely on the support.

6. A grinding wheel comprising a rotatable support, a plurality of .abrasive segments removably mounted thereon and forming a grinding surface, each segment having bevelled clamping shoulders and an inner supporting face, a shoe of cement, hardened from a plastic condition into intimate and integral contact with the inner face on each segment, which has a seating surface premolded against that portion of the support upon which it ultimately rests in the assembled structure and conforming exactly to the shape thereof, and clamping devices engaging said shoulders and adjustably securing the segments on the support with the cement shoes seated correctly in spaced relationship thereon.

7 The method of making a grinding wheel having abrasive segments removably mounted on a' rotatable support comprising the steps of providing the segments with spacing shoes of compressible material, mounting the segments with these shoes in contact with said support, molding a layer of plastic self-hardening material between the segment and the support, compressing said spacing shoes and forcing said moldable material into full contact with the inner face of the segment and the adjacent portion of the support, permitting the moldable material to harden and finally clamping the segments to the support with their shoes contacting with those portions of the support to which they have been molded.

8. The method of making a grinding wheel having abrasive segments removably mounted on a rotatable drum which is provided with a peripheral supporting surface comprising the steps of placing a settable adhesive plastic layer of cementitious material on the seating surface of each segment, locating each segment in its ultimate correct position on said supporting surface of the drum and causing the cement to harden while in contact with both the abrasive segment and said drum, and thereby form a seating shoe integral with the segment, and thereafter adjustably securing the segments to the drum with the shoes in the same positions in which they were molded.

Signed at Worcester, Massachusetts, this 19th day of December 1928.

HUGO W. H. BETH. 

